A conventional gas turbine engine consists of an air compressor, a combustor, and a turbine. Air is drawn into the engine and its pressure is increased by the compressor. The air then enters the combustor where fuel is added and burned, thus adding energy and raising the temperature of the air. This heated compressed gas flows through a turbine where energy is extracted by the turbine blades. This energy transfer spins the turbine rotor, making the energy available as power on the rotating shaft. Part of this power is used to drive the compressor, while the remainder is transferred to the output shaft where it is available to drive whatever equipment is desired. In a simple-cycle gas turbine, this process is approximately 26% efficient, since much of the energy input in the fuel is not transferred into output energy on the shaft. Some of the energy is lost to mechanical inefficiencies and friction, but the majority leaves the engine in the turbine exhaust and is last up the stack.
It has been common practice in modern gas turbines to provide a regenerator or recuperator to capture some of the energy in the exhaust and return it to the engine. In the regenerator, which is simply a large air-to-air heat exchanger, the energy in the hot turbine exhaust gas is transferred to the compressed air before it enters the combustor. This process raises the temperature of the compressed air, so that the amount of fuel energy needed to heat the air passing through the turbine is consequently less and the resulting fuel savings make the engine a more efficient power source.
Although the above-described regenerative system is commonly used with modern gas turbines, there are literally thousands of gas turbines in existence that are operating well, but inefficiently, because they are originally not provided with such a regenerative system. Attempts to provide regenerative systems to older gas turbines have been attempted in the past, but difficulties have been encountered in providing the equipment because of the cost of doing so. In most cases, a gas turbine that was originally designed as a simple-cycle turbine does not readily lend itself to a conversion to a regenerative cycle, because of the difficulty and major redesign process required to pipe cool air to the regenerator and to return the heated air to the combustion section of the turbine. In addition, the older gas turbines sometimes have other equipment located around them that prevents the introduction of the ducting and piping required if they are to be provided with a regenerative system. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.
It is, therefore, an outstanding object of the invention to provide a regenerative system for use as a retro-fit to certain simple-cycle gas turbines.
Another object of this invention is the provision of a regenerative system for relatively inexpensively converting simple-cycle gas turbines to more efficient prime movers.
A further object of the present invention is the provision of a retro-fit regenerative system which is simple in construction, which is inexpensive to manufacture, and which is capable of a long life of useful service.
It is another object of the instant invention to provide a retro-fit system for converting a gas turbine to a regenerative system in which the cost of doing so is paid back by higher efficiency in the turbine over a short period of time.
A still further object of the invention is the provision of a retro-fit regenerative system for application to gas turbines in which the equipment can be added without affecting the structural integrity of the turbine and without major modification to existing casings and other pieces of equipment.
It is a further object of the invention to provide a retro-fit regenerative system for a gas turbine in which the down-time during installation is very short.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.